This study is involved with the development of total hip joint prostheses capable of functioning without failure for a lifetime of servie. The study addresses itself to: 1. Evaluation of fatigue characteristics of metallic materials in use, 2. Study of biocompatibility of presently used and new potentially used materials, 3. Study of carcinogenesis of prosthetic materials, 4. Development of a new bio-assay technique, 5. Studies of wear and development of wear resistant materials; a polyethylene-graphite composite has been developed and is under evaluation at present, 6. Studies of fixation to bone using porous materials; a fiber metal composite has been developed and is evaluated in relation to this application, 7. Finite element model computer studies of the prosthetic devices to derive the ideal design configurations and materials selection.